JP6623780B2 - Clad plate, method for producing the same, and equipment for induction heating cooker - Google Patents

Description

  The present invention relates to a clad plate and an appliance for an induction cooking device.

  Induction heating cookers (hereinafter referred to as "IH cookers") have been widely used as cooking heat sources that do not use flames and have high heat generation efficiency, and are particularly suitable for elderly houses and high-rise buildings where fire safety is required. In stores and houses, it has become an indispensable equipment. In addition, IH rice cookers occupy the mainstream of rice cookers because they can cook rice deliciously by rapid heating characteristics using the high heat power of IH, and boast a high penetration rate including general households.

  Except for a special case such as an all-metal compatible IH cooker, a vessel such as a pot cooker used in an IH cooker has a heating element made of a magnetic metal material arranged to face the IH coil. Conventionally, ferritic stainless steel or ordinary steel has been used as the heating element. Unless a magnetic metal material is used as the heating element, a general IH cooker cannot be heated in the first place, and a magnetic metal material is used even in the case of a special heating method such as an all-metal compatible IH cooker. This is because the heat generation efficiency is extremely reduced as compared with the case and the power consumption is increased.

  For this reason, utensils for IH cookers have a two-layer structure in which a magnetic metal material made of ferritic stainless steel or ordinary steel is arranged on one surface (outer surface) and aluminum is arranged on the other surface (inner surface). Those having a three-layer structure in which stainless steel is further disposed on the inner layer surface have been generally used.

  However, ferritic stainless steel and ordinary steel as magnetic metal materials used for the heat generating layer are more likely to rust than high corrosion resistant materials such as austenitic stainless steel. For this reason, in some cases, it is necessary to apply a coating process such as a clear coat on the surface of the magnetic metal material, and the cost cannot be denied.

  In addition, when ferritic stainless steel is used as a heating element for a high-grade object, a polishing step called roping to remove a surface pattern that occurs when the molding process is performed on the object requires a polishing process. Earring, which is a phenomenon in which the length of the surplus flange portion is not uniform, occurs, and there is a problem that the material yield is reduced.

  In Patent Literature 1, the inner surface layer of the pan is made of titanium or a titanium alloy, and the outer surface layer of the pan is made of a magnetic metal material, particularly, austenitic ferrite duplex stainless steel (SUS329J1) which is a magnetic stainless steel, and used as a heat generating layer. A clad pan for an electromagnetic cooker that is capable of performing high-efficiency, wide-ranging cooking by using the material as a material for alleviating heat conduction and is lightweight is disclosed.

  Patent Document 2 discloses that austenitic / ferritic duplex stainless steel is used as a composite material, carbon steel or alloy steel is used as a base material, and production costs are minimized. An inexpensive clad steel sheet that can suppress the expansion of the diffusion layer is disclosed.

  Further, Patent Document 3 discloses a chemical composition containing, by mass%, C: 0.01 to 0.04%, Ni: 1.0 to 2.0%, and Cr: 20.0 to 22.0%. The difference between the 0.2% proof stress in the 0 ° direction and the 90 ° direction with respect to the rolling direction is less than 20 MPa, and the surface roughness Rz in the rolling direction and the 90 ° direction is 0.5 to 4 μm. Discloses an austenitic ferritic stainless steel sheet for press forming having an earring ratio of less than 2% and a small earring.

JP-A-8-96946 JP 2013-209688 A Patent No. 5656435

  The invention disclosed in Patent Document 1 aims at providing a lightweight clad pan for an electromagnetic cooker that is highly efficient and capable of cooking over a wide range and is lightweight. Neither the corrosion resistance nor the drawability can be improved.

  The invention disclosed by Patent Document 2 aims at joining a clad steel sheet having austenitic / ferritic duplex stainless steel as a composite material and a carbon steel or alloy steel as a base material by a hot joining method, According to this invention, neither the corrosion resistance nor the drawability of the heat generating layer can be improved.

  Further, the invention disclosed in Patent Document 3 aims at improving the deep drawability of a single plate of austenitic / ferritic duplex stainless steel in a single plate, and in the first place, the corrosion resistance and draw formability of the heat generating layer of the clad plate. It does not aim to improve.

  An object of the present invention is to improve the workability of forming objects and the corrosion resistance of the outer layer surface as compared with a conventional clad plate using a ferritic stainless steel or ordinary steel as a heat generating layer. An object of the present invention is to provide a clad plate and an IH cooking appliance that are suitably used as materials for appliances such as a pot used in an IH cooking appliance including a cooking appliance.

  The inventor of the present invention has made intensive studies to solve the above-mentioned problems, and as a result, conventionally, austenitic-ferritic duplex stainless steel which has not been conventionally used as a material for IH cooker by joining with pure aluminum or aluminum alloy. We paid attention to. Then, the austenitic / ferritic duplex stainless steel is joined to pure aluminum or an aluminum alloy by an efficient and simple method using a warm rolling joining method in the atmosphere, thereby forming an exothermic layer (outer layer surface). A clad plate comprising an austenitic / ferritic duplex stainless steel and pure aluminum or an aluminum alloy as a heat transfer layer (inner surface) can be provided, and it has been found that the above problems can be solved. did. The present invention is as listed below.

(1) A clad plate used as a material for forming a device for an induction heating cooker,
An IH heating layer made of austenitic / ferritic duplex stainless steel, and a heat transfer layer made of pure aluminum or an aluminum alloy joined to the IH heating layer,
The IH heat generating layer is ,
C: 0.005 to 0.060%,
N: 0.10 to 0.30%,
Si: more than 0% and 1.0% or less,
Mn: 0.5-6.0%,
Ni: 1.0 to 10%,
Cr: 19.0 to 28.0%,
Mo: 0 to 4.0%,
Cu: 0 to 2.0%,
The balance: consists of Fe and impurities,
The Cr equivalent defined by the following formula (1) exceeds 21% by mass, and the ratio of the Cr equivalent to the Ni equivalent defined by the following formula (2) (Cr equivalent / Ni equivalent) is 2.0 to 3. and has a chemical composition which is 0, have a metal structure area ratio of the ferrite phase is 40% to 70%,
A clad plate in which the maximum deviation of the flange radius is less than 8 mm when the bottom surface is circular with a diameter of 200 mm and the shape of the pot is drawn so as to have a height of 120 mm .
Cr equivalent (% by mass) = Cr content (% by mass) + Mo content (% by mass) + 1.5 × Si content (% by mass) (1)
Ni equivalent (% by mass) = Ni content (% by mass) + 30 × (C content (% by mass) + N content (% by mass)) + 0.5 × Mn (% by mass) + 0.5 × Cu (% by mass)・ ・ ・ ・ ・ (2)

  (2) The clad plate according to item 1, comprising two layers, the IH heat generation layer and the heat transfer layer.

(3) a protective layer bonded to the front Kiden thermal layer, further comprising,
2. The clad plate according to claim 1, wherein the protective layer is made of austenitic stainless steel or austenitic-ferritic duplex stainless steel.

( 4 ) In the chemical composition of the austenitic-ferritic duplex stainless steel of the IH heating layer, the total content of Mn, Ni, Cr, Mo, and Cu is 30% by mass or less.
4. The clad plate according to any one of items 1 to 3 .

(5) A drawing of the clad plate according to any one of 1-4, wherein, having the IH heating layer as an inner layer of the heat transfer layer and having as an outer layer, the IH heating layer An appliance for an induction heating cooker having a thickness of 0.3 mm or more and an area ratio of a ferrite phase of the IH heating layer of 40% or more.
(6) used as a molding material for induction heating cookware;
An IH heating layer made of austenitic / ferritic duplex stainless steel, and a heat transfer layer made of pure aluminum or an aluminum alloy joined to the IH heating layer,
The IH heat generating layer is,
C: 0.005 to 0.060%,
N: 0.10 to 0.30%,
Si: more than 0% and 1.0% or less,
Mn: 0.5-6.0%,
Ni: 1.0 to 10%,
Cr: 19.0 to 28.0%,
Mo: 0 to 4.0%,
Cu: 0 to 2.0%,
The balance: consists of Fe and impurities,
The Cr equivalent defined by the following formula (1) exceeds 21% by mass, and the ratio of the Cr equivalent to the Ni equivalent defined by the following formula (2) (Cr equivalent / Ni equivalent) is 2.0 to 3. A clad plate having a chemical composition of 0 and a metal structure in which an area ratio of a ferrite phase is 40 to 70%,
A method for producing a clad plate, wherein the duplex stainless steel is subjected to an intermediate heat treatment at a temperature in the range of 900 to 1100 ° C. during cold rolling to produce the clad plate.
Cr equivalent (% by mass) = Cr content (% by mass) + Mo content (% by mass) + 1.5 × Si content (% by mass) (1)
Ni equivalent (% by mass) = Ni content (% by mass) + 30 × (C content (% by mass) + N content (% by mass)) + 0.5 × Mn (% by mass) + 0.5 × Cu (% by mass)・ ・ ・ ・ ・ (2)

By performing cold rolling on the hot coil produced by hot rolling, in producing austenitic-ferritic duplex stainless steel,
By performing at least two times of cold rolling at a rolling reduction of 20% or more as the cold rolling, and performing at least one intermediate heat treatment at 900 to 1100 ° C. between the at least two times of cold rolling. The austenitic / ferritic duplex stainless steel described in any one of the above items 5 to 5 can be produced.

  According to the present invention, there is provided a clad plate having an austenitic ferrite duplex stainless steel as a heat generating layer and pure aluminum or an aluminum alloy as a heat transfer layer. This clad plate can be produced efficiently using the warm rolling method in the atmosphere, and has a better formability for forming objects than conventional clad plates using ferritic stainless steel as the heating layer. It is suitable for use as a material for IH cooking utensils since it has excellent corrosion resistance and the outer layer surface of the utensils has excellent corrosion resistance.

FIG. 1 is an explanatory diagram showing earrings generated during deep drawing.

  An embodiment for carrying out the present invention will be described together with the principle of the present invention. In the following description, “%” regarding the chemical composition means “% by mass” unless otherwise specified.

1. Principle of the present invention (1-1) Austenitic / Ferritic Duplex Stainless Steel Austenitic / ferritic duplex stainless steel is defined by SUS329J1, SUS329J3L, SUS329J4L in, for example, JIS G4305 cold-rolled stainless steel sheet and steel strip (2012). It is a high corrosion resistant material having corrosion resistance equal to or higher than that of austenitic stainless steel.

  Further, in recent years, an alloy-saving austenitic / ferritic duplex stainless steel which realizes high corrosion resistance equivalent to that of austenitic stainless steel while suppressing raw material costs has been developed. For example, Japanese Patent Application Laid-Open No. 61-56267, International Publication 2002/2002 It is disclosed in the pamphlet No. 27056, the pamphlet of International Publication No. 1996/18751, the specification of Japanese Patent No. 534070, and the like, and is standardized in ASTM-A240 as S32304, S32101, and S82122.

  Until now, these austenitic-ferritic duplex stainless steels have been used mainly as thick plates of several mm thick in harsh corrosive environments such as chemical plants and seawater environments. It has been unsuitable for processing applications. For this reason, austenitic-ferritic duplex stainless steel has not received much attention as a material for constituting utensils for IH cookers.

  The austenitic / ferritic duplex stainless steel can have a part of the metal structure as a magnetic ferrite structure by appropriately selecting its chemical composition and heat treatment during the manufacturing process. In the present invention, the chemical composition of the austenitic / ferritic duplex stainless steel used as the heat generating layer of the utensil for the IH cooker is such that the Cr equivalent is represented by Cr content + Mo content + 1.5 × Si content, and the Ni equivalent is Ni content. + 30 × (C content + N content) + 0.5 × Mn content + 0.5 × Cu content, in mass%, the Cr equivalent exceeds 21%, and the ratio of Cr equivalent to Ni equivalent (Cr equivalent / Ni equivalent) is in the range of 2.0 to 3.0, and the area ratio of the ferrite phase in the metal structure is in the range of 40 to 70% in the state of being used as a product as a product. Used.

  Here, the fact that the Cr equivalent exceeds 21% and the ratio (Cr equivalent / Ni equivalent) is in the range of 2.0 to 3.0 means that the area ratio of the ferrite phase in the metal structure is 40 to 70%. It is necessary to adjust to the range and to enable IH heat generation by the magnetism of the ferrite phase.

  When the area ratio of the ferrite phase of the austenitic / ferritic duplex stainless steel used is less than 40%, the magnetism required for the IH heating layer cannot be secured, and the heating in the IH cooker becomes unstable. When the area ratio of the ferrite phase is more than 70%, the area ratio of the austenite phase decreases, so that the high corrosion resistance characteristic of the austenitic / ferritic duplex stainless steel is impaired. This results in a surface pattern due to roping peculiar to the stainless steel.

  Here, the final heat treatment temperature for producing the austenitic / ferritic duplex stainless steel may be determined according to the chemical composition of each stainless steel, but is generally in the range of 900 ° C to 1100 ° C.

(1-2) Cladding of austenitic / ferritic duplex stainless steel with pure aluminum or aluminum alloy Next, in order to use austenitic / ferritic duplex stainless steel as a material for constituting an appliance for an IH cooker, austenitic / ferritic stainless steel is used. A method of clad bonding between duplex stainless steel and pure aluminum or an aluminum alloy will be described.

  In general, there are methods of joining cladding materials for equipment, such as explosion bonding, cast-in, welding overlay, and rolling, but for industrial mass production of clad plates, joining by rolling is suitable. Among them, cold or warm rolling bonding that does not require hot rolling in an assembled slab is suitable.

  In addition, it is necessary to use a metal having excellent thermal conductivity for the heat transfer layer. Among these metals, a special aluminum or aluminum alloy that can be softened by heating in a relatively low temperature range is used. Since a warm rolling joining method capable of joining in the air without the need for a vacuum facility or an atmosphere heating furnace can be applied, a desirable manufacturing process can be realized from the viewpoint of capital investment and facility maintenance.

  As a result of conducting various trial production tests and examining the conditions for manufacturing a clad plate by joining austenitic / ferritic duplex stainless steel and pure aluminum or an aluminum alloy by such a warm rolling joining method, 100 to 500 were previously determined. The target clad plate can be obtained by laminating both material plates heated to 0 ° C. immediately before the joining rolling mill and rolling and joining in a range of 10 to 50% as a total reduction ratio of all the material thicknesses. It has been found.

  In this case, the reason why both the material plates are preliminarily heated to 100 to 500 ° C. is to lower the deformation resistance of the aluminum material in particular by heating and to promote a new surface by spreading by joining rolling. If the heating temperature is lower than 100 ° C., the deformation resistance cannot be reduced, and if the heating temperature is higher than 500 ° C., a thick oxide film is formed particularly on the surface of the austenitic / ferritic duplex stainless steel to inhibit interfacial bonding. Not preferred.

  Heating only one of austenitic / ferritic duplex stainless steel and pure aluminum or an aluminum alloy is not desirable because the effect of heating cannot be obtained due to heat removal due to superposition immediately before joining rolling.

  In addition, rolling and joining in a range of 10 to 50% as a total reduction ratio of all the material thicknesses, in addition to the effect of developing a new surface by rolling and expanding as described above, This is because the surfaces are brought into close contact with each other by the rolling pressure and joined. When the rolling reduction is less than 10%, the appearance of a new surface and the effect of crimping cannot be obtained, and when the rolling reduction exceeds 50%, the deformation of the material becomes too large to be non-uniform, and continuous joining is performed. In addition to impairing the properties, the load on the rolling mill also increases.

(1-3) IH cooker dish The austenitic ferrite duplex stainless steel thus produced and pure aluminum or an aluminum alloy clad plate are formed into a pot shape and processed as an IH cooker dish. In order to use it, it was drawn into a pot shape with a low surface: a circle having a diameter of 200 mm and a height: 120 mm, and the possibility of heat generation when heated using a commercially available IH cooker was investigated.

  As a result, the austenitic / ferritic duplex stainless steel, which is the heat generating layer after ladle forming, has a thickness of 0.3 mm or more, and the area ratio of the ferritic phase as the austenitic / ferritic duplex stainless steel is 40% or more. In some cases, it has been found that stable IH heating is possible as in the case of a vessel using a conventional ferritic stainless steel as a heating element. This is because when the thickness of the austenitic / ferritic duplex stainless steel, which is the heating layer, is less than 0.3 mm, or when the area ratio of the ferrite phase is less than 40%, the magnetism of the heating layer becomes insufficient and the IH cooker becomes inoperable. This is because the object cannot be recognized as a magnetic metal.

  Considering that the austenitic ferritic duplex stainless steel, which is the heat generating layer, has a thickness of 0.3 to 1.0 mm and a total thickness of the clad plate of 1.0 to 5. Desirably, it is about 0 mm.

  As described above, when a vessel for an IH cooker is made using a clad plate having two layers, the interior surface of the vessel is made of pure aluminum or an aluminum alloy, but a high-strength, highly corrosion-resistant protective layer is provided on the interior surface of the vessel. In the case of providing further, in addition to the duplex stainless steel and pure aluminum or aluminum alloy, a layer made of austenitic / ferritic duplex stainless steel or austenitic stainless steel is provided on the surface facing the inside of the pan, and a total of three layers are provided. A clad plate made of

  Furthermore, regarding the moldability to the pot shape as a vessel, the presence or absence of roping that impairs the appearance of the surface after molding, the occurrence of earrings that cause a decrease in material yield during pot molding, and the press load that indicates the mechanical load during press working Was evaluated from the following three points.

(A) Roping First, the appearance of the surface after molding was evaluated using a prototype of a pot having a low surface: a circle having a diameter of 200 mm and a height: 120 mm, which was previously produced. The outer layer made of ferritic stainless steel used for conventional IH cooking utensils has a problem of forming a roping pattern. However, the austenitic / ferritic duplex stainless steel having the chemical composition and the area ratio of the ferrite phase described above is used. No roping pattern was observed in the pot molding using steel as the outer layer surface, and it was found that a beautiful surface could be obtained. This is effective for omitting the polishing step after the molding and the additional coating treatment.

(B) Earring FIG. 1 is an explanatory diagram showing a state of an earring generated during deep drawing.

  In the case of the earring, since the elongation and deformation of the flange portion are not uniform on the circumference during the deep drawing in the pot shape, the number of parts that must be cut and removed increases, causing a deterioration in the material yield.

  A test was conducted to investigate the amount of earrings generated. A circular sample having a diameter of 80 mm was collected from a 2.0 mm thick clad plate obtained by joining S82122 austenitic ferrite duplex stainless steel and pure aluminum specified by ASTM-A240, and was deep-deformed with a cylindrical punch having a diameter of 40 mm. A draw test was performed at a draw ratio of 2.0 by drawing, and the ear ratio he of the obtained deep drawn product (in FIG. 1, (P1 to P4 average height−V1 to V4 average height) / (Average height of P1 to P4 and V1 to V4) × 100 (%) was evaluated. Table 1 shows the results.

  As shown in Table 1, the amount of generated earring was different depending on the manufacturing history of the austenitic / ferritic duplex stainless steel material used. When a 0.6 mm thick sheet obtained by one cold rolling and finishing heat treatment from a hot rolled austenitic / ferritic duplex stainless steel sheet is used as the cladding material, the ear ratio is 9.9%. Large earrings occurred. Since this large earring is removed as an unnecessary portion when the object is formed, the material yield is reduced.

  Therefore, we focused on the manufacturing process of the duplex stainless steel plate used for the clad bonding material and examined various improvement measures. During the cold rolling from the hot-rolled hot coil to the target plate thickness, at least one intermediate It has been found that the heat treatment reduces the ear ratio indicating the strength of the earring. The temperature of the intermediate heat treatment may be in the range of 900 to 1100 ° C. as the material temperature.

(C) Press load As for the press load representing the mechanical load during the press working, a circular sample having a diameter of 80 mm is sampled from a clad plate having a thickness of 2.0 mm, and is subjected to deep drawing with a cylindrical punch having a diameter of 40 mm. It evaluated by the press load at the time of. Table 2 shows the results.

  As shown in Table 2, the press load of the clad plate using the austenitic / ferritic duplex stainless steel for the heat generating layer was equal to or greater than the press load of the clad plate using the austenitic stainless steel. Austenitic / ferritic duplex stainless steel does not undergo work-induced martensitic transformation as seen in quasi-austenitic stainless steels such as SUS304, but has low work hardening, but is annealed by solid solution strengthening due to the high content of alloying elements. The strength as it is tends to increase.

  The chemical composition of the austenitic / ferritic duplex stainless steel is adjusted mainly by the substitutional elements composed of five elements of Mn, Ni, Cr, Mo and Cu, and the higher the content of these alloy elements, the higher the strength. For this reason, the strength of the austenitic / ferritic duplex stainless steel can be reduced by suppressing the total content of these substitutional elements to a small value.

  That is, when it is desired to reduce the press load for the purpose of reducing the mechanical load during the press working, the total of Mn, Ni, Cr, Mo and Cu is limited within the range of the relational expression between the Cr equivalent and the Ni equivalent described above. The press load can be reduced by controlling the content to 30% by mass or less.

  The lower limit of the total content of Mn, Ni, Cr, Mo and Cu is preferably 21% or more from the viewpoint of adjusting the area ratio of the ferrite phase in the duplex stainless steel to a target range.

2. Cladding Plate According to the Present Invention (2-1) Overall Configuration The cladding plate according to the present invention uses austenitic / ferritic duplex stainless steel as an IH heating layer which is an outer layer surface of an IH cooking appliance. A heat transfer layer serving as an outer layer surface of the object has a structure of two or more layers having a layer made of pure aluminum or an aluminum alloy.

  That is, the clad plate according to the present invention comprises, in order from the outer layer surface side of the IH cooking appliance, a two-layer structure having a heating layer made of austenitic / ferritic duplex stainless steel and a heat transfer layer made of pure aluminum or an aluminum alloy. Or a clad plate composed of three layers further having a protective layer composed of an austenitic / ferritic duplex stainless steel or an austenitic stainless steel layer on the inner layer side of an IH cooking appliance.

(2-2) IH heating layer The heating layer in the clad plate according to the present invention is required to have high corrosion resistance while having magnetism. Austenitic stainless steel cannot be used for the heat generating layer because it is non-magnetic, and ferritic stainless steel cannot be used because it is not magnetic but has high corrosion resistance. Therefore, an austenitic / ferritic duplex stainless steel is used for the heating layer.

  As an austenitic / ferritic duplex stainless steel, the Cr equivalent is expressed as Cr content + Mo content + 1.5 × Si content from the mass% of its chemical composition, and Ni equivalent is Ni content + 30 × (C content + N Content) + 0.5 × Mn content + 0.5 × Cu content, the Cr equivalent exceeds 21 and the ratio (Cr equivalent / Ni equivalent) is in the range of 2.0 to 3.0. In addition, a steel having an area ratio of a ferrite phase in a range of 40 to 70% in a state used for a product can be used.

  Here, the condition that the Cr equivalent exceeds 21 and the ratio of Cr equivalent / Ni equivalent is in the range of 2.0 to 3.0 is necessary for adjusting the area ratio of the ferrite phase to the range of 40 to 70%. When the area ratio of the ferrite phase is less than 40%, it is not possible to secure magnetism necessary for heating in an IH cooker as a heating layer, and when the area ratio of the ferrite phase exceeds 70%, It is unsuitable for spoiling the high corrosion resistance characteristic of austenitic / ferritic duplex stainless steel and for producing surface patterns due to roping when formed into articles.

  Further, when it is desired to reduce the press load required for press molding of the container, the chemical composition of the austenitic / ferritic duplex stainless steel is set to 30% by mass as the total content of Mn, Ni, Cr, Mo and Cu. It can be adjusted to be within mass%.

  Here, the chemical composition of the austenitic / ferritic duplex stainless steel used for the IH heating layer will be described in detail.

  C has a strong influence on the above-mentioned Ni equivalent and is used to adjust the stability of the austenite phase. However, if contained excessively, it precipitates Cr carbide and deteriorates corrosion resistance. Is desirably 0.060%. Further, in order to extremely reduce the C content, the cost of the steel refining process is significantly increased. Therefore, the lower limit of the C content is preferably set to 0.005%.

  N, like C, strongly affects the Ni equivalent and is an element used for adjusting the stability of the austenite phase. In addition, since the effect of improving corrosion resistance can be obtained by containing N, the content of N can be more positively contained than that of C, and it is preferable to contain 0.10% or more. However, an excessive N content causes precipitation of Cr nitride in a heat-affected zone due to a heat treatment step or welding, so the upper limit of the N content is preferably set to 0.30%.

  Si is used as a deoxidizing element in the refining process in some cases, and is contained to some extent, and also has an effect on the Cr equivalent. However, if it exceeds 1.0%, the material becomes hard. Therefore, it is desirable that the Si content be 1.0% or less. Since the lower limit of the Si content depends on the amount used, it usually exceeds 0%. However, if it is 0.1% or more, an amount sufficient to exert an effect as a deoxidizing agent can be used.

  Mn is an element that contributes to stabilization of the austenite phase and has a similar effect and is less expensive than Ni. However, there is a disadvantage that the corrosion resistance is degraded due to an excessive content exceeding 6.0% or the hot workability is impaired. Therefore, the Mn content is desirably 0.5 to 6.0%.

  Ni is a typical austenite phase stabilizing element, and although it is expensive as a raw material cost, is an element having characteristics that hardly cause deterioration of corrosion resistance and hot workability even when contained excessively. Therefore, it is desirable to contain 1.0% or more, but it is desirable to keep the upper limit to 10% from the viewpoint of cost.

  Cr is an important element for ensuring the corrosion resistance of stainless steel, and the austenitic / ferritic duplex stainless steel used in the present invention needs to have a Cr equivalent of more than 21 and therefore contains 19.0% or more. It is desirable. However, since excessive content causes hot working cracks, it is desirable to set the upper limit of the Cr content to 28.0%.

  Mo may be contained as necessary to show a great effect on the improvement of the corrosion resistance of steel. However, since the raw material cost is significantly increased, the upper limit of the Mn content is preferably set to 4.0%. .

  Cu is an element that contributes to the stabilization of the austenite phase, like Ni and Mn, and may be contained as necessary. However, if it exceeds 2.0%, it impairs hot workability. It is desirable that the Cu content be 2.0% or less.

  Other chemical components contain P, S, etc. as impurities, but are acceptable as long as the effects of the present invention are not impaired.

(2-3) Heat transfer layer A metal having excellent thermal conductivity is used for the heat transfer layer, and pure aluminum (JIS 1000 system) or aluminum which can be used in the production of a clad plate by a warm joining rolling method in the air. Alloys (JIS 2000 (Al-4Cu), 3000 (Al-1Mn), 4000 (Al-12Si), 5000 (Al-2Mg), 6000 (Al-1Mg-Si), 7000 (Al-Mn) 5Mn-Mg-Cu)).

  However, it is desirable to use JIS 3000 series (Al-1Mn) and 5000 series (Al-2Mg) as the aluminum alloy from the viewpoint of securing the deep drawing workability in the cold and avoiding the age hardening due to the heat treatment. .

(2-4) Protective Layer The protective layer is formed for the purpose of protecting the electric heating layer, and a generally used resin protective layer is used.

  On the other hand, when a metal is used as the protective layer, high corrosion resistance is required at an appropriate strength, but since the protective layer does not need to be a magnetic material, austenitic stainless steel can be used. Of course, austenitic ferrite duplex stainless steel may be used.

(2-5) Thickness of Each Layer The thickness configuration of each material constituting the clad plate can be arbitrarily selected according to the form of the target object. In consideration of use as an appliance for an IH cooker, the thickness of the IH heating layer is preferably 0.3 to 1.0 mm, the thickness of the heat transfer layer is preferably 0.5 to 3.0 mm, and the total The thickness is desirably about 1.0 to 5.0 mm.

  This is because if the thickness of the austenitic / ferritic duplex stainless steel is less than 0.3 mm, the efficiency during IH heating is impaired, and if it exceeds 1.0 mm, the generated heat can be efficiently transmitted to the heat transfer layer. It is not possible. The thickness of the heat transfer layer only needs to be sufficient to spread the heat generated by the IH coil to the whole object, but if the thickness of the heat transfer layer is less than 0.5 mm, a sufficient heat transfer effect is obtained. If the thickness exceeds 3.0 mm, the heat capacity of the container itself increases and the heat generation efficiency is impaired.

3. Method for producing austenitic / ferritic duplex stainless steel Austenitic / ferritic duplex stainless steel used as a material for joining the clad plate of the present invention has a rolling ratio of, from a hot coil produced by hot rolling, in the production process. In order to adjust to a target thickness by performing cold rolling of 20% or more at least twice, at least one intermediate heat treatment is performed in the range of 900 ° C to 1100 ° C between at least two cold rollings. By performing the intermediate heat treatment, earrings generated when the clad plate is formed into a vessel can be reduced, and the material yield can be increased.

4. IH cooking utensil The IH cooking utensil according to the present invention is a drawn compact of the clad plate according to the present invention, which has an IH heat generating layer as an outer layer and a heat transfer layer as an inner layer.

  When the austenitic ferrite duplex stainless steel as the IH heat generating layer has a thickness of 0.3 mm or more and the area ratio of the ferrite phase as the austenitic ferrite duplex stainless steel is 40% or more, the conventional method is used. Stable IH heating is possible in the same manner as a vessel using ferritic stainless steel as a heating element. If the thickness of the austenitic / ferritic duplex stainless steel, which is the heating layer, is less than 0.3 mm, or if the area ratio of the ferrite phase is less than 40%, the magnetism of the heating layer becomes insufficient and the IH cooker magnetizes the dishes. Cannot be recognized as body metal.

  INDUSTRIAL APPLICABILITY The IH cooking utensil according to the present invention can be manufactured at a low cost by efficient production, and is superior in corrosion resistance of the outer layer surface as compared with a conventional clad plate using a ferritic stainless steel as a heating layer.

  As a material of the heat generating layer constituting the cladding plate for the IH cooker, a mass-produced material of a hot-rolled annealed plate having a chemical composition shown in Table 3 was obtained, and a cold-rolled and annealed 0.6 mm-thick plate was obtained. A spread annealing plate was obtained.

Further, the cold-rolled annealed plates listed below were prepared as a material of the heat transfer layer constituting the clad plate for an IH cooker.
(I) A1100P pure aluminum specified in JIS H 4000 (2006) and a cold-rolled annealed plate having a thickness of 2.2 mm (ii) A 3004P aluminum alloy specified in JIS H 4000 (2006) and a thickness of 2.2 mm Cold rolled annealed plate

  A laminate obtained by laminating these materials was heated to 350 ° C., and then joined and rolled by a laboratory mill to obtain a clad plate having a total thickness of 2.0 mm. The obtained clad plate was subjected to press working, drawn into a pot shape having a low surface: a circle having a diameter of 200 mm and a height: 120 mm, and subjected to a heating test using a commercially available IH cooker. In this case, the evaluation was good when stable continuous heating was possible with the IH cooker.

  Further, in order to evaluate the corrosion resistance of the outer layer surface (heating layer) of the obtained clad plate, a salt spray test was performed in accordance with JIS Z 2371 (2000), and the rating number was determined from the appearance after continuous exposure for 200 hours. The evaluation was determined to be high corrosion resistance based on a rating number of 10.

  Three evaluation tests were performed on the press formability of the obtained clad plate.

  That is, the clad plate was pressed and drawn into a pot shape having a low surface of a circular shape having a diameter of 200 mm and a height of 120 mm, and the presence or absence of a roping pattern was determined from the appearance. Furthermore, the maximum deviation of the flange radius was measured from the flange shape of the pan obtained in order to evaluate the amount of earrings generated, and the case where the deviation was less than 8 mm was determined to be good.

  The press load was evaluated based on the press load when a draw test was performed at a draw ratio of 2.0 by deep-drawing a circular sample having a diameter of 80 mm of the clad plate with a punch having a diameter of 40 mm. Desirable pressing load at this time was 6.0 ton or less, which is the pressing load when SUS304 is used as the material of the outer layer surface.

  The test results are summarized in Table 4.

  Sample No. 1 to 9 are the results of the pot in which the clad plate of the present invention was formed, and good results were obtained in any of the evaluations of corrosion resistance, earring, roping, press load, and IH heating.

  Sample No. Reference numerals 10 and 11 are comparative examples. In the manufacturing process of the austenitic / ferritic duplex stainless steel used as the heating layer, the conditions of the intermediate heat treatment are different from those specified in the present invention. Earrings occurred, and a deviation of 8 mm or more occurred in the flange radius.

  Sample No. 12 is a comparative example using an austenitic / ferritic duplex stainless steel having a ferrite phase ratio of less than 40% as a heating layer. However, since the magnetism of the heating layer was insufficient, the control of the IH cooker was stopped during heating and was not completed. It became stable.

  Sample No. No. 13 is a comparative example using an austenitic / ferritic duplex stainless steel having a ferrite phase area ratio of more than 70% as a heat generating layer. In the salt water spray test, spot-like rust was observed, and high corrosion resistance was obtained. In addition, the appearance after forming was unsatisfactory because a roping pattern occurred on the outer surface of the forming pot.

  Sample No. 14 to 17 are comparative examples using an austenitic stainless steel, which is a nonmagnetic metal, for the heat generating layer. However, although the outer layer surface has good corrosion resistance, deep drawability, and appearance, it is nonmagnetic. Heating was impossible with a general IH cooker.

Further, the sample No. Reference numeral 18 is a comparative example in which a ferrite-based stainless steel, which is a magnetic metal, is used as a heat generating layer as a conventional example. Although it is possible to perform IH heating satisfactorily, the outer layer surface is inferior in corrosion resistance, and the flange radius due to the earring is reduced. Deviations and appearance patterns due to roping occurred.

Claims (6)

A clad plate used as a molding material for induction heating cooker equipment,
An IH heating layer made of austenitic / ferritic duplex stainless steel, and a heat transfer layer made of pure aluminum or an aluminum alloy joined to the IH heating layer,
The IH heat generating layer is ,
C: 0.005 to 0.060%,
N: 0.10 to 0.30%,
Si: more than 0% and 1.0% or less,
Mn: 0.5-6.0%,
Ni: 1.0 to 10%,
Cr: 19.0 to 28.0%,
Mo: 0 to 4.0%,
Cu: 0 to 2.0%,
The balance: consists of Fe and impurities,
The Cr equivalent defined by the following formula (1) exceeds 21% by mass, and the ratio of the Cr equivalent to the Ni equivalent defined by the following formula (2) (Cr equivalent / Ni equivalent) is 2.0 to 3. and has a chemical composition which is 0, have a metal structure area ratio of the ferrite phase is 40% to 70%,
A clad plate in which the maximum deviation of the flange radius is less than 8 mm when the base is drawn into a pot shape having a circular shape with a diameter of 200 mm and a height of 120 mm .
Cr equivalent (% by mass) = Cr content (% by mass) + Mo content (% by mass) + 1.5 × Si content (% by mass) (1)
Ni equivalent (% by mass) = Ni content (% by mass) + 30 × (C content (% by mass) + N content (% by mass)) + 0.5 × Mn (% by mass) + 0.5 × Cu (% by mass)・ ・ ・ ・ ・ (2)   The clad plate according to claim 1, comprising two layers, the IH heating layer and the heat transfer layer. The protective layer bonded to the front Kiden thermal layer, further comprising,
The clad plate according to claim 1, wherein the protective layer is made of austenitic stainless steel or austenitic-ferritic duplex stainless steel. 4. The chemical composition of the austenitic-ferritic duplex stainless steel of the IH heating layer, wherein a total content of Mn, Ni, Cr, Mo, and Cu is 30% by mass or less. 5. The clad plate described in 1. A has been clad plate aperture formed body according to any one of claims 1-4, having the IH heating layer as an inner layer of the heat transfer layer and having as an outer layer, the thickness of the IH heating layer Is 0.3 mm or more, and the area ratio of the ferrite phase of the IH heating layer is 40% or more.   Used as a molding material for induction heating cooker equipment,
  An IH heating layer made of austenitic / ferritic duplex stainless steel, and a heat transfer layer made of pure aluminum or an aluminum alloy joined to the IH heating layer,
  The IH heat generating layer is,
  C: 0.005 to 0.060%,
  N: 0.10 to 0.30%,
  Si: more than 0% and 1.0% or less,
  Mn: 0.5-6.0%,
  Ni: 1.0 to 10%,
  Cr: 19.0 to 28.0%,
  Mo: 0 to 4.0%,
  Cu: 0 to 2.0%,
  The balance is composed of Fe and impurities,
  The Cr equivalent defined by the following formula (1) exceeds 21% by mass, and the ratio of the Cr equivalent to the Ni equivalent defined by the following formula (2) (Cr equivalent / Ni equivalent) is 2.0 to 3. A method for producing a clad plate having a chemical composition of 0 and a metal structure in which an area ratio of a ferrite phase is 40 to 70%,
  A method for producing a clad plate, wherein the duplex stainless steel is subjected to an intermediate heat treatment at a temperature in the range of 900 to 1100 ° C. at the time of cold rolling.
  Cr equivalent (% by mass) = Cr content (% by mass) + Mo content (% by mass) + 1.5 × Si content (% by mass) (1)
  Ni equivalent (% by mass) = Ni content (% by mass) + 30 × (C content (% by mass) + N content (% by mass)) + 0.5 × Mn (% by mass) + 0.5 × Cu (% by mass)・ ・ ・ ・ ・ (2)

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